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Message-ID: <a7f1f8f5-075c-4b77-8ab6-c19546037c43@yandex.ru>
Date: Sat, 2 Nov 2024 15:24:31 +0300
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Subject: Re: Vacuum statistics
To: Alexander Korotkov <aekorotkov@gmail.com>
Cc: Ilia Evdokimov <ilya.evdokimov@tantorlabs.com>,
 Andrei Zubkov <zubkov@moonset.ru>,
 pgsql-hackers <pgsql-hackers@postgresql.org>, a.lepikhov@postgrespro.ru,
 jian he <jian.universality@gmail.com>
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 <c82e7776-7841-42a0-9247-878584174750@tantorlabs.com>
 <4a902cea-54fb-41b5-b208-b84731a5f577@postgrespro.ru>
 <CACJufxHb_YGCp=pVH6DZcpk9yML+SueffPeaRbX2LzXZVahd_w@mail.gmail.com>
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Content-Language: en-US
From: Alena Rybakina <lena.ribackina@yandex.ru>
In-Reply-To: <eb64c0cd-afbb-45fe-9baf-dd9555ae36ac@postgrespro.ru>
Archived-At: <https://www.postgresql.org/message-id/a7f1f8f5-075c-4b77-8ab6-c19546037c43%40yandex.ru>
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Hi!

On 29.10.2024 14:02, Alena Rybakina wrote:
> On 28.10.2024 16:40, Alexander Korotkov wrote:
>> On Sun, Aug 25, 2024 at 6:59 PM Alena Rybakina
>> <a.rybakina@postgrespro.ru>  wrote:
>>> I didn't understand correctly - did you mean that we don't need SRF if
>>> we need to display statistics for a specific object?
>>>
>>> Otherwise, we need this when we display information on all database
>>> objects (tables or indexes):
>>>
>>> while ((entry = ScanStatSnapshot(pgStatLocal.snapshot.stats, &hashiter))
>>> != NULL)
>>> {
>>>       CHECK_FOR_INTERRUPTS();
>>>
>>>       tabentry = (PgStat_StatTabEntry *) entry->data;
>>>
>>>       if (tabentry != NULL && tabentry->vacuum_ext.type == type)
>>>           tuplestore_put_for_relation(relid, rsinfo, tabentry);
>>> }
>>>
>>> I know we can construct a HeapTuple object containing a TupleDesc,
>>> values, and nulls for a particular object, but I'm not sure we can
>>> augment it while looping through multiple objects.
>>>
>>> /* Initialise attributes information in the tuple descriptor */
>>>
>>>    tupdesc = CreateTemplateTupleDesc(PG_STAT_GET_SUBSCRIPTION_STATS_COLS);
>>>
>>> ...
>>>
>>> PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
>>>
>>>
>>> If I missed something or misunderstood, can you explain in more detail?
>> Actually, I mean why do we need a possibility to return statistics for
>> all tables/indexes in one function call?  User anyway is supposed to
>> use pg_stat_vacuum_indexes/pg_stat_vacuum_tables view, which do
>> function calls one per relation.  I suppose we can get rid of
>> possibility to get all the objects in one function call and just
>> return a tuple from the functions like other pgstatfuncs.c functions
>> do.
>>
> I haven’t thought about this before and agree with you. Thanks for the 
> clarification! I'll fix the patch this evening and release the updated 
> version.

I updated the patches as per your suggestion. You can see it here [0].

[0] 
https://www.postgresql.org/message-id/85b963fe-5977-43aa-9241-75b862abcc69%40postgrespro.ru

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    <p>Hi!<br>
    </p>
    <div class="moz-cite-prefix">On 29.10.2024 14:02, Alena Rybakina
      wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:eb64c0cd-afbb-45fe-9baf-dd9555ae36ac@postgrespro.ru">
      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
      <div class="moz-cite-prefix">On 28.10.2024 16:40, Alexander
        Korotkov wrote:<br>
      </div>
      <blockquote type="cite"
cite="mid:CAPpHfdvSo3mfH=2m4ADCHAuN=22SnBY3TrPaPbGKTw3r_Jaw7Q@mail.gmail.com">
        <pre class="moz-quote-pre" wrap="">On Sun, Aug 25, 2024 at 6:59 PM Alena Rybakina
<a class="moz-txt-link-rfc2396E" href="mailto:a.rybakina@postgrespro.ru"
        moz-do-not-send="true">&lt;a.rybakina@postgrespro.ru&gt;</a> wrote:
</pre>
        <blockquote type="cite">
          <pre class="moz-quote-pre" wrap="">I didn't understand correctly - did you mean that we don't need SRF if
we need to display statistics for a specific object?

Otherwise, we need this when we display information on all database
objects (tables or indexes):

while ((entry = ScanStatSnapshot(pgStatLocal.snapshot.stats, &amp;hashiter))
!= NULL)
{
     CHECK_FOR_INTERRUPTS();

     tabentry = (PgStat_StatTabEntry *) entry-&gt;data;

     if (tabentry != NULL &amp;&amp; tabentry-&gt;vacuum_ext.type == type)
         tuplestore_put_for_relation(relid, rsinfo, tabentry);
}

I know we can construct a HeapTuple object containing a TupleDesc,
values, and nulls for a particular object, but I'm not sure we can
augment it while looping through multiple objects.

/* Initialise attributes information in the tuple descriptor */

  tupdesc = CreateTemplateTupleDesc(PG_STAT_GET_SUBSCRIPTION_STATS_COLS);

...

PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));


If I missed something or misunderstood, can you explain in more detail?
</pre>
        </blockquote>
        <pre class="moz-quote-pre" wrap="">Actually, I mean why do we need a possibility to return statistics for
all tables/indexes in one function call?  User anyway is supposed to
use pg_stat_vacuum_indexes/pg_stat_vacuum_tables view, which do
function calls one per relation.  I suppose we can get rid of
possibility to get all the objects in one function call and just
return a tuple from the functions like other pgstatfuncs.c functions
do.

</pre>
      </blockquote>
      I haven’t thought about this before and agree with you. Thanks for
      the clarification! I'll fix the patch this evening and release the
      updated version.<br>
      <span style="white-space: pre-wrap">
</span>
      <pre class="moz-signature" cols="72">
</pre>
    </blockquote>
    <p>I updated the patches as per your suggestion. You can see it here
      [0].</p>
    <p>[0]
<a class="moz-txt-link-freetext" href="https://www.postgresql.org/message-id/85b963fe-5977-43aa-9241-75b862abcc69%40postgrespro.ru">https://www.postgresql.org/message-id/85b963fe-5977-43aa-9241-75b862abcc69%40postgrespro.ru</a><br>
    </p>
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